The present invention relates to information recording/reproducing apparatuses, and more particularly, to an apparatus which records information on an optical disc recorded with an address mark to identify which one of two addresses is an address for groove or an address for land, and reproduces information from the optical disc.
The magneto-optical disc has attracted much attention as a rewritable recording medium having a large storage capacity and high reliability, and has been reduced to practice for use for example as a computer memory. With increase in the amount of information and development of more compact devices, there is a demand for a recording/reproducing techniques which allows for higher density.
The high density recording/reproducing techniques involves a technique on the apparatus side and a technique on the medium side. One of high density recording/reproducing techniques on the former side is a method of optical recording by superresolution which permits light collected spot exceeding the limit of laser beam diffraction by optical super resolution with a shielding member inserted in the optical path. One such approach is for example disclosed in detail in xe2x80x9cHigh Density Optical Recording by Supperresolutionxe2x80x9d, Yamanaka et al., Japanese Journal of Applied Physics, Vol. 28 (1989), Supplement 28-3, pp. 197-200. The latter technique includes reducing the pitch of a medium and improving reproducing resolution by the use of a magnetic multi-layer film. The technique of improving the reproducing resolution takes advantage that a Gaussian distribution of the temperature of a light collected spot is maximized in the vicinity of the center and the state of a recorded layer is selectively transferred to a reproducing layer for reading the state of the reproducing layer.
In a recently developed, so-called land-groove type magneto-optical disc, grooves are wobbled to record a synchronizing clock and an address for recording and reproducing. When a groove is wobbled to record an address, the address for the groove can be recorded, but an address for a land can be hardly recorded. Therefore, the applicant has proposed a method of sequentially recording addresses for both groove and land by wobbling the groove, thereby recording an address mark to identify which one of the two addresses is an address for groove or an address for land in a previously filed international application (International Application No. PCT/JP97/02442, the international filing date of which is Jul. 14, 1997).
According to the technique, a groove is wobbled, so that not only an address for a groove but also an address for a land can be recorded. However, specific techniques to record/reproduce a data signal to/from such a magneto-optical disc has not been suggested.
It is therefore an object of the present invention to provide an information recording apparatus which can surely record information to a recording medium recorded with an address mark and an information reproducing apparatus which can surely reproduce information from a recording medium recorded with an address mark.
An information recording apparatus according to the present invention includes detection means to detect an address mark and recording means to record information on a recording medium in synchronization with the detected address mark. The detection means preferably includes an optical head and an address mark synchronous signal generation means. The optical head includes a laser to direct a beam to a recording medium and outputs an address mark signal in response to an address mark. The address mark synchronous signal generation means generates an address mark synchronous signal in synchronization with an address mark in response to an address mark signal. The recording means includes a magnetic head, magnetic head driving means, and laser driving means. The magnetic head driving means drives the optical head in synchronization with an address mark synchronous signal. The laser driving means drives the laser in synchronization with an address mark synchronous signal. More preferably, the address mark is recorded by forming a wobble on at least one sidewall of a groove. The optical head outputs a wobble signal in response to a wobble. The detection means further includes a phase synchronizing circuit and synchronizing means. The phase synchronizing circuit generates a clock signal in synchronization with the wobble in response to the wobble signal. The synchronizing means synchronizes the clock signal with an address mark synchronous signal. The magnetooptical head driving means drives the magnetic head in response to the synchronized clock signal. The laser driving means drives the laser in response to the synchronized clock signal.
In the information recording apparatus, an address mark recorded on a recording medium is detected, and an address mark signal is output from the optical head based on the address mark and an address mark synchronous signal is generated in synchronization with the address mark signal. The magnetic head and laser are driven in synchronization with the address mark synchronous signal. More specifically, a wobble signal is output from the optical head based on a wobble formed on a sidewall of a groove, and a clock signal in synchronization with the wobble is generated in response to the wobble signal. The clock signal is synchronized with an address synchronous signal and the magnetic head and laser are driven in response to the synchronized clock signal. Thus, information may be surely recorded on a recording medium in synchronization with the address mark.
An information reproducing apparatus according to the present invention includes detection means to detect an address mark and reproducing means to reproduce information from a recording medium in synchronization with the detected address mark. The detection means preferably includes an optical head and address mark synchronous signal generation means. The optical head includes a laser to direct a beam upon the recording medium, and outputs an address mark signal based on an address mark. The address mark synchronous signal generation means generates an address mark synchronous signal in synchronization with an address mark in response to the address mark signal. The reproducing means includes laser driving means to drive a laser in synchronization with an address mark synchronous signal. More preferably, the address mark is recorded by forming a wobble on at least one sidewall of a groove. The optical head outputs a wobble signal based on a wobble. The detection means further includes a phase synchronizing circuit and synchronizing means. The phase synchronizing circuit generates a clock signal in synchronization with a wobble in response to a wobble signal. The synchronizing means synchronizes a clock signal with an address mark synchronous signal. The laser driving means drives the laser in response to the synchronized clock signal.
In the information reproducing apparatus, an address mark recorded on a recording medium is detected, and an address mark signal is output based on the address mark from the optical head. An address mark synchronous signal in synchronization with the address mark is generated in response to the address mark signal, and the laser is driven in synchronization with the address mark synchronous signal. More specifically, a wobble signal is output from the optical head based on a wobble formed on a sidewall of a groove, and a clock signal in synchronization with the wobble is generated in response to the wobble signal. The clock signal is synchronized with the address mark synchronous signal, and the laser is driven in response to the synchronized clock signal. Thus, information can be surely reproduced from the recording medium.